1. Field of the Invention
The present invention relates to a method of making an electrochemical device; and, more specifically, to a method of making n electrochemical device encompassing batteries such as lithium ion secondary batteries and electrochemical capacitors such as electric double layer capacitors.
2. Related Background Art
Electrochemical devices represented by batteries such as lithium ion secondary batteries and electrochemical capacitors such as electric double layer capacitors are easy to reduce their size and weight, and thus are expected to become power supplies and backup power supplies for portable devices (small-size electronic devices) and auxiliary power supplies for hybrid cars, for example.
As the electronic devices further reduce their sizes, the electrochemical devices are desired to become thinner. Known as means for yielding such an electrochemical device which can be made thinner is a method of preparing structures each of which comprises a pair of electrode layers and a separator layer of a porous film disposed therebetween and is dipped in an electrolytic solution; thermocompression-bonding the structures together; and producing an electrochemical device from thus obtained electrochemical element (e.g., Japanese Patent Publication No. 3297034).
If the separator and electrode layers are to be laminated after being individually dipped in the electrolytic solution in such a manufacturing method, their alignment for lamination will be very difficult because of a decrease in the strength of the separator layers, etc. It is therefore considered important that the electrode and separator layers be partly bonded together with a hot-melt adhesive beforehand and then be dipped in the electrolytic solution and thermocompression-bonded together. One of reasons why the alignment must be done accurately is that, for example, lithium ions released from a positive electrode are deposited without being taken into a negative electrode in a lithium second battery and thus lower the battery capacity unless the negative electrode opposes the whole surface of the positive electrode.